Documentation for choosing specific colors

I didn’t see a way to do this in the spec. I’d be happy to write some documentation if someone could explain how to do this.

For example, how can I ensure that black is used for time_of_day == 'night' and gold for time_of_day == 'morning'?

Chart(data).mark_area().encode(
    color='time_of_day:N',
    x='frame:Q',
    y='movement:Q',
)

[jakevdp]

You can do this by specifying the Scale for the color encoding. There’s an example near the end of the Seattle Weather Tutorial.

For your chart, it might look something like this:

from altair import Chart, Color, Scale

Chart(data).mark_area().encode(
    Color('time_of_day:N',
          scale=Scale(domain=['night', 'morning'],
                      range=['black', 'gold'])),
    x='frame:Q',
    y='movement:Q',
)

If you would like to add a section on this in the config documentation, that would be a nice contribution!

[getup8]

Just wanted to document an almost identical way, but aligned with what’s in the docs.

tableau10 can be any of these: https://vega.github.io/vega/docs/schemes/#categorical

# Define your custom theme.
def my_theme():
    return {
        'config': {
            'range': {'category': {'scheme': 'tableau10'}}
        }
    }

# Register and enable.
alt.themes.register('my_theme', my_theme)
alt.themes.enable('my_theme')